Approximately 79 million US adults suffer from hypertension, of which 47% are considered to have treatment resistant hypertension (patients using 3+ antihypertensive medicines). A major factor contributing to the progression of treatment resistant hypertension is sympathetic nerve hyperactivity, which results in enhanced vascular adrenergic stimulation, increased vasoconstriction, and high blood pressure. Recent attempts to disrupt excessive sympathetic nerve innervation to arterial smooth muscle cells (SMCs) is highlighted by ongoing clinical trials of renal artery nerve denervation, suggestive of dysfunctional vasomotor tone following sympathetic stimulation. In resistance arteries, vasoconstriction is controlled by sympathetic nerve innervation to smooth muscle cells (SMCs) by direct binding of norepinephrine to cell surface alpha1- adrenergic receptors (alpha1-ARs). Subsequently, this causes vasoconstriction signaling events within SMCs mediated by heterotrimeric G-proteins, inositol triphosphate, and serine/threonine kinases. However, growing evidence implicates an undefined role for Src family tyrosine kinases (SFKs) in regulating adrenergic stimulated vasoconstriction. Recently, our laboratory has published work showing that Pannexin1 (Panx1), a novel ATP release channel, is only expressed on SMCs of resistance arteries and functionally couples with alpha1-AR mediated vasoconstriction, but not with other vasoconstrictors (e.g., endothelin-1). Pharmacological and genetic inhibition of a specific Panx1 intracellular loop motif containing a tyrosine residue (Y198), located within a putative Src kinase homology 2 domain, severely inhibits ATP release, channel activity, and vasoconstriction. Based on these data, we hypothesize that a unique tyrosine kinase mediated alpha1-AR signaling pathway exists in SMCs of resistance arteries that regulates vasoconstriction through activation of Panx1 by Src family kinase phosphorylation. Aim 1 of this proposal will determine if SFKs regulate vasoconstriction by alpha1-AR stimulation in resistance arteries and modulate the phosphorylation of Panx1 at the intracellular loop motif (Y198) using mouse thoracodorsal and mesenteric arteries. Aim 2 of the proposal will assess if Panx1 Y198 phosphorylation is enhanced in alpha1-AR stimulated responses in resistance arteries of treatment resistant hypertensive humans compared with normotensive patients, and test the clinical importance of the novel Y198 inhibitory peptide (PanX) to vasoconstrictor properties of human arteries. This work aims to elucidate an unexplored tyrosine kinase signaling pathway that potentiates sympathetic nerve hyper-activation and pathological SMC contraction in treatment resistant hypertension.